This is a §371 of PCT/EP2004/001920 filed Feb. 26, 2004, which claims priority from German Patent Application No. 103 08 891.1 filed Feb. 28, 2003.
Trimeric cyclic ketone peroxides are known. In 1968 P. Story (JACS 90, 817 (1968)) discovered a method for producing macrocyclic hydrocarbons and lactones from tricycloalkylidene peroxides by pyrolysis. Hence tricycloalkylidene peroxides are valuable starting materials for preparing these classes of compounds which are otherwise very difficult to produce.
Tricyclohexylidene peroxide (trimeric, cyclic cyclohexanone peroxide) is particularly in demand for the synthesis of cyclopentadecane and hexadecanolide which are starting materials for musk perfumes.
In DE 21 32 616 P. Story discloses a two-step method for producing tricyclo-alkylidene peroxides. He prepares a 1-hydroperoxy-1′-hydroxy-dicycloalkylidene peroxide from cycloalkanone, hydrogen peroxide and acid and converts it further with strong acids to form the desired cyclic compound. Trimers and dimers are formed in this process approximately in a ratio of 75:25 in yields of <60% based on the cycloalkanone that was used.
The handling of these solid peroxides which are very sensitive to friction and shock is a safety risk.
Harding and Whalen (Industrial and Engineering Chemistry, Product Research Development 1975, vol. 14, No. 4, p. 232-239) published a study on the preparation of trimeric, cyclic cyclohexanone peroxide and investigated the direct preparation of cyclohexanone and hydrogen peroxide without isolating open-chain intermediate products. They were able to avoid the risk of handling solid peroxides by working in solvents (high-boiling hydrocarbons). They optimized the conditions of synthesis (type and amount of solvent, acid and temperature) in extensive experiments. Under the best conditions they obtained trimeric cyclic cyclohexanone peroxide in a yield of 84% in addition to 1 to 7% and on average 4% dimers. The reaction time at about 20° C. was 22 hours. The most suitable acids proved to be 70% perchloric acid and concentrated hydrochloric acid. The use of sulfuric acid resulted in substantially longer reaction times.
They strongly advised against the use of nitric acid because of the danger of forming unstable pernitric acid.
The disadvantages of this method are the use of 70% perchloric acid (dangerous, expensive) or concentrated hydrochloric acid (corrosive; chlorine can be formed with hydrogen peroxide), the use of a large quantity of acetic acid as a solubilizer (250 g/mol cyclohexanone, waste water pollution!) and the long reaction time which makes a batch process uneconomical and makes it practically impossible to carry out a continuous process.
Hence there is a need to create a method for producing trimeric ketone peroxides which as selectively as possible (without large amounts of dimers) results in a high yield, a short reaction time and as little waste as possible and also enables a continuous operation.
Hence the object of the invention is to create a method which has the stated advantages.
This is achieved according to the invention by a method for producing trimeric ketone peroxides by reacting cyclic or open-chain ketones with H2O2 in the presence of an acidic catalyst in a suitable solvent which is characterized in that nitric acid is used as the catalyst.